On Thursday 31 July 2025 at 01:02 UTC, a SYN flood targeted a healthcare portal customer in Western Europe. The attack peaked at 63.1 Gbps and lasted 181 minutes. Traffic originated from 3097 autonomous systems in 69 countries, predominantly hijacked home routers.
| Vector | SYN flood |
| Peak | 63.1 Gbps |
| Duration | 181 min |
| Time to mitigation | 0.452 s |
| Attack traffic reaching origin | 0.087% |
| Legitimate traffic challenged | 0.80% |
Timeline
The attack was preceded by an extortion email received two days earlier. Edge packet filters identified the flood by source port and payload signature and dropped it at line rate across 20 points of presence.
What the customer saw
No customer-visible impact. The on-call engineer was notified and acknowledged the incident from the dashboard.
Recommendations
- Lower challenge thresholds on authentication endpoints during high-risk events.
- Enable authenticated origin pulls.
- Review allow-listed partner ranges quarterly.
Nice to read a vendor blog that admits what went wrong.
Clear and practical, thanks.
How do you avoid challenging uptime monitors and partners?
Great write-up. We saw almost the same pattern on our login endpoint last month.
Verified good bots and allow-listed partners bypass challenges entirely.
Would love a follow-up on how you handle HTTP/3 fingerprinting.